A win last time out saw the hosts move within six points of the top seven in the Eastern Conference, while their visitors have just a one-point gap to bridge to seventh-placed Los Angeles Galaxy
Match preview
After starting the MLS season in positive fashion, with their opening five games producing nine points, Chicago Fire went on to endure a particularly tough run of form.
Ezra Hendrickson's side went on to pick up just two points from the next nine outings, as they scored eight goals and conceded 19 times in the slump consisting of seven defeats and two draws.
The Illinois outfit were finally able to put an end to that winless run with a narrow triumph over DC United, before bouncing back from a defeat to Houston Dynamo with a victory by the same scoreline at home to Philadelphia Union.
Two further losses then followed to drag Hendrickson's men back towards the foot of the table, but they were successful in returning to winning ways last time out, as a Jhon Muran brace made the difference in a 2-0 home victory over Toronto.
Having now leapfrogged the Reds and climbed up to 12th place, Hendrickson will look to build a run and cut the six-point gap to the playoffs with another positive result at the weekend.
They meet a Seattle Sounders side who find themselves far more involved in the playoff fight in their Conference, having only just dropped out of the top seven.
Following a relatively underwhelming start to the season, the Sounders put themselves in the leading pack of their division with a strong run of form across May and June, picking up five wins and 16 points from a span of seven outings.
A narrow defeat to CF Montreal then followed, before Brian Schmetzer's side instantly rebounded with a 2-0 win away at Toronto thanks to goals from Dylan Teves and Fredy Montero.
Looking to build another hot streak on the back of that triumph, Seattle hosted Portland Timbers but were comfortably beaten 3-0, before Hany Mukhtar hit the only goal in their contest away at Nashville SC to condemn the Sounders to a second straight defeat.
Having now dropped out of the playoff places as a result of those losses, Schmetzer's men will be keen to ensure the gap between themselves and the top seven does not stretch any further and will instead look to bounce back to winning ways to retake their place in the leading pack.
Chicago Fire Major League Soccer form:
Seattle Sounders Major League Soccer form:
Team News
After securing a crucial win against Toronto last time out, Chicago Fire could come into Sunday's game with an unchanged starting XI.
Their line will again be led by 18-year-old Jhon Duran, who marked his second consecutive start with a decisive brace in that game after providing an assist in each of the previous two outings.
Further back, former Liverpool star Xherdan Shaqiri will continue to offer support to the front man, likely playing in the middle of a supporting trio.
Seattle Sounders will remain without experienced forward Raul Ruidiaz, who has spent a lengthy spell on the sidelines after scoring five goals in his first nine league appearances of the season.
In his absence, the line should again be led by Fredy Montero, with Cristian Roldan and joint-top scorer Jordan Morris providing threat from the wings.
Xavier Arreaga could return to the team from the outset, having come off the bench last time out following an injury scare.
Chicago Fire possible starting lineup:
Slonina; Sekulic, Teran, Czichos, Bornstein; Navarro, Pineda; Mueller, Shaqiri, Gutierrez; Duran
Seattle Sounders possible starting lineup:
Cleveland; Gomez, Arreaga, Tolo; A Roldan, Lodeiro, Rusnak, Medranda; C Roldan, Montero, Morris
We say: Chicago Fire 1-1 Seattle Sounders
Given the differing form of the two sides, Sunday's game seems particularly tough to call, and we see a share of the spoils as the most likely outcome.